why is my mesh fully lit from all angles with no lights in the scene?
The World Background itself (grey) is also a source of lighting. To remove its influence, change the Color to black in the box on the right, or set the Strength to 0

This can also happen if you forget to connect your material to a shader before connecting to the material output:

This example just uses a Diffuse BSDF - note that despite the object no longer &quot;glowing&quot;, it is still lit, even though there is no light in the scene - that is from the World Background as mentioned at the top: